diff --git a/nyquist/dspprims.lsp b/nyquist/dspprims.lsp
index e05005fa7..67eb8f645 100644
--- a/nyquist/dspprims.lsp
+++ b/nyquist/dspprims.lsp
@@ -342,11 +342,9 @@
 
 ; convenient biquad: normalize a0, and use zero initial conditions.
 (defun nyq:biquad (x b0 b1 b2 a0 a1 a2)
-  (if (< a0 1.0) 
-    (error (format T "a0 < 1 in biquad~%"))
-    (let ((a0r (/ 1.0 a0)))
-      (snd-biquad x (* a0r b0) (* a0r b1) (* a0r b2) 
-                               (* a0r a1) (* a0r a2) 0 0))))
+  (let ((a0r (/ 1.0 a0)))
+    (snd-biquad x (* a0r b0) (* a0r b1) (* a0r b2) 
+                             (* a0r a1) (* a0r a2) 0 0)))
 
 
 (defun biquad (x b0 b1 b2 a0 a1 a2)
@@ -366,6 +364,8 @@
 
 ;; NYQ:LOWPASS2 -- operates on single channel
 (defun nyq:lowpass2 (x hz q)
+  (if (or (> hz (/ (snd-srate x) 2.0))(< hz 0))
+    (error "frequency out of range" hz))
   (let* ((w (* 2.0 Pi (/ hz (snd-srate x))))
          (cw (cos w))
          (sw (sin w))
@@ -383,6 +383,8 @@
   (multichan-expand #'nyq:highpass2 x hz q))
 
 (defun nyq:highpass2 (x hz q)
+  (if (or (> hz (/ (snd-srate x) 2.0))(< hz 0))
+    (error "frequency out of range" hz))
   (let* ((w (* 2.0 Pi (/ hz (snd-srate x))))
          (cw (cos w))
          (sw (sin w))